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With some pain in my heart i will try to show you how we successfully build in the HFS4 v2 in the engine bay. It's with great sadness that after the test day, i returned home and an hour later my car was stolen.

I'll write the build here, so at least that was not a total loss.

First of all, a warning. I never planned to use more than 50% meth. I highly doubt that this setup is good for 100% meth. It's very flammable and i'm not comfortable with my BOV opening up to excrete methanol vapor. Bad things are going to happen.

I build in the kit in two days. The first day we concentrated on the hardware part, the second day we tweaked some of the hardware and did all the testing so it's ready to be tuned. I own a E91 Touring, and i did not want a tank in my trunk, meaning the pump will go in the engine bay and the water meth tank will be my windshield whiper tank (WW tank). This is NOT AT ALL how Richard designed this setup.

Moreover, when it came to find a place to fit the HFS4 controller, i decided to put it in the ECU box. Again, NOT AT ALL how Richard suggests to do it, as it may be more prone to malfunction due to condensed water.

So my setup is far from ideal, but all in all still workable. The write up may hint to some pitfalls and interesting solutions if you are also looking for an engine bay mount using the WW tank. Obviously neither Richard nor I are in any way, shape of form responsible for any damage done by trying to copy the work i did. This is merely a write up to show you how i did it. I strongly suggest that if you can, stick to Richard's instructions in the manual, which differs here and there from my setup.

Having said that, let's begin.

What kind of tools did we use, what was involved ?
First of all, it is imperative that you read the manual and study the wiring diagram. It doesn't take very long and will make you more efficient. I also suggest you don't do this installation alone if you're not very experienced. I had two friends help with the hardware, both with an automotive engineering background. I myself am just a hobbyist.

We used regular shop tools and did not need access to the bottom of the car, so you could do this in any dry place. you'll need to cut/solder some wires in your ECU box and tap signals. In our case i think it's 5. Please refer to Richard's diagram below for the 335i.

You'll need to take the right wheel off so you'll need tools for that and a jack.
You'll need small and medium sized tie wraps !

We used the 8 and 10mm wrench, soldering equipment, heat shrinks to seal the wire, insulation tape, duct tape (never leave home with out), 22 / 23 mm drill (for the holes in the WW tank), drill for tap hole 11/32" (8.8 mm) of the nozzles in the chargepipe, some self tapping metal screws, and a 2 mm drill to secure the pump to a custom made bracket which fits an existing arch shape in the engine bay (see pics).

My specific setup
As the pic shows, i have the dual cone intakes, which give a bit more breathing space under the hood for the nozzles and the lines. I also have the CP-E chargepipe. I decided to place the nozzles DOWNSTREAM of the MAF sensor, as some experts claim the injection may create incorrect readings of the MAF sensor and you don't want that during WOT. It's a choice i guess and each setup has pros and cons.

ECU Assembly

The white ECU plastic cover can be a little tricky to get off. there are two clips on the two opposite sides and two slides on the other sides. You don't need any tools to open it, patience will do.
I did not do this myself. You need to take your time to find the right wires and is clear from the diagram above. When it comes time to test (so the jumper in the controller is on SYS), make sure do DO connect also the green USER wire, as it has the (only) signal linking to pedal position (which is actually the fuel injector signal).

Because i told Richard to preset/solder the controller for the BMW N54, it saved my the hassle of setting that up. (the second part of the diagram above). So the only wire cutting or soldering is on 5 wires or so.

I think i used fuse 9 (which was not connected) to get the power for the gauge and the controller.

The ground signal from the controller was also taken from a ground signal out of the ECU.

Gauge

To get that casing out, you first need to clear the insulation and rubber around the shifter. No tools required, just wiggle/slide/turn until it comes off. It's stretchable, so it's an easy job. Next is to get the middle console cover out. You can take two credit cards and slide them at the driver's side AT THE BACK of the console. On the pic above you can see that side lifted already a bit. By putting a screwdriver between the credit cards you can pry it open without damaging the top, which is quite delicate. once you have your fingers underneath you can then find the other clips one by one and get the whole cover off. Once that's done you have simple access to the glasses compartment which i've build in the gauge.

I chose to put the gauge in the small compartment just above the shifter. I (rather cruedly) cut out some of the plastic and also removed some of the rubber of the pad so the gauge would be kept in place by friction. It took some reiteration, but i was happy with the end result. I have no pic of that. We fed the gauge cable from the controller thru a hole in the air vent. It took some time to wiggle it in there and get it into the fuse box, but it's a great place for it.

the cable from the controller to the gauge needs also a little trial and error. But moving thru the vents as shown made us straightforward, protected from water and more importantly removed the necessity to find and cut thru existing fire walls.

Fast Acting Valve - FAV

The FAV was not correctly assembled out of the box. We had to redo it, otherwise the line wouldn't fit on it. Here's a pic of it sitting on the chargepipe using a tie wrap.

Pump
There's only one place we could find to fit the pump.
There's a strong arch holding the power steering oil and we cut a bit of it underneath to make room for the pump. It's secured by two screws on the chasis. Regretfully, one was fully eroded and broke when trying to loosen it. After shrugging shoulders and after talking to Richard we revisited the pump install and decided to cut an extra piece of aluminium so at least all 4 screws of the pump (with rubber padding) were secured to the metal arch.

The location of the arch near the wheel seemed secure enough not to get too wet, something Richard expressed his concerns about.
Notice that the pump is upside down (the power cable is at the bottom) and I therefore also wrapped some insulation tape around it, to keep moist from entering the pump.

The pump takes significant power. Because it uses a relais, we took the power straight from the dynamo. Power is only fed to the pump when the controller also has power. Using fuse 9 you make sure that when the car is off, no power goes to the pump (or controller).

WW tank
It's a nightmare to take this out. the WW tank is located on the right side of the car towards the door, behind the wheel arch. The tank itself is actually arched to fit there. You'll need to take out the side blinker. You push it towards the engine or the opposite way, just try both, and when you think you're about to break it, you'll feel some movement. By sliding it a bit more, you can then pull it towards you. It's held in place by friction. And doing a good job of that... When reinstalling the WW tank, make sure you use a little bit of tape to the cable for the blinker, so you can easily reconnect it back to the light.

You'll need to take the wheel off and there's A LOT of screws to unbolt. They're all easy, just remember how it all fits back, you don't want to have spare parts when you're done...
Once the side blinker and all the bolts and wheel arch casing parts are out of the way, the WW tank itself is visible. Now you'll have to get it out. It's not easy, but basically it comes towards the front of the engine. I had to use some force acquired from a lack of patience after fiddling with it for 20 minutes. Getting it back was easier. The unit has a pumps on it, i reckon one for the WW and one for the Xenon lights. I drilled the third spot with the 22/23 mm drill for the HFS4 meth intake. it fits neatly and the filter also fits:

Don't forget to clean the tank with water when you have it out. Also test your setup for leaks before you reinstall it.

Chargepipe
As mentioned, we drilled DOWNSTREAM from the MAP sensor. I decided to go with the 2 x 1.0 mm nozzles:

Don't forget the loctite. the cp-e chargepipe was pretty thin. Maybe three smaller nozzles would also be a good idea and put them in a circle around the chargepipe, so the spray is as uniform around the pipe as possible. You don't want one cylinder to get more water than the other. Richard's point is that for this fact you should give the water more time to evaporate by getting it more UPSTREAM towards the intercooler. I was just very afraid of a false MAP sensor reading.

One of the tap in the chargepipe was at best one rotation. It would be an improvement to weld in a thicker piece in which you could drill more tap. However, we managed to get it to work without leakage and it felt tight and strong enough.

Securing wires
Remember that dual cones move around A LOT on high speed. keep wires securely in place using tie wraps and away from hot or moving parts. You do not want a rupture with high flammable meth while you're drving or racing...

Testing the unit
As i said, because our cars have direct injection, the green USER cable also needs to be connected when testing:
The purging of the pump is pretty easy with a bucket. We did a a couple of times.
Now is also a good time to turn the dial on the gauge called "SC" which tweaks the amount of bars against the fuel injector sensor signal. I think we had it set at about 11 o'clock. You can do it when you're testing the spray pattern, as Richard explains in his manual in test 3.

The HFS4 comes with dummies to plug into the nozzle holes of the charge pipe.

Then you get ready to spray against the windshield, we used ducttape:

We did not yet set up the failsafes, because we still needed to tune. there's a jumper to bypass the failsafes, we had it set ON (so bypass the failsafe settings on the gauge).

the Thres dial inside the controller was the last thing we set. For our application, it turned out you need to turn it almost completely counter clock wise (so setting it very low/sensitive). I would say we had to set it to 3 o'clock and minimum is 4 o'clock. If Thres is not set correctly, you'll be doing your test drive, do a WOT, but no or little spray is seen.

Final notes:

- The gauge actually has an ON/OFF button. Very handy but hard to notice when you look at the gauge.
- The pump vibrates a lot, so make sure you use all 4 screws to secure it.
- Direct injection needs the green USER connector to the controller in the SYS jumper during initial testing.
- Make sure that you stick to the test procedure as descibred. Don't skip the tests.